take a utility knife and cut a V out of the dash along the cracks. Get some expanding foam (not the triple expanding), and fill in the cracks. Wait about ahour for it to completely dry and harden then use a razor lay it flat on the dash and work it around till you have the foam trimmed off at dash level, then rough it up / level it out with some sand paper. Then at some autoparts stores you can get a dash repair kit that has the plastic filler that dries to the texture of the dash, then use some of that fusion plastic paint.
I got a maroon dash off ebay for $87, so bought it. In my project truck I might do the foam stuff, then I'm color chaning it from tan to grey.